scholarly journals Analysis of space-based observations of peroxyacetyl nitrate (PAN) and its relation to other atmospheric tracers

2021 ◽  
Author(s):  
Bruno Franco ◽  
Lieven Clarisse ◽  
Cathy Clerbaux ◽  
Pierre-François Coheur
Keyword(s):  
Time Series ◽  
Spatial Distribution ◽  
Tropospheric Chemistry ◽  
Boreal Summer ◽  
Peroxyacetyl Nitrate ◽  
Ozone Monitoring Instrument ◽  
Source Regions ◽  
Comprehensive Picture ◽  
The Tropics ◽  
Atmospheric Tracers

<p>Peroxyacetyl nitrate (CH<sub>3</sub>C(O)O<sub>2</sub>NO<sub>2</sub>; abbreviated as PAN) is the main tropospheric reservoir of nitrogen oxide radicals (NO<sub>x</sub>) and contributes to redistributing NO<sub>x</sub> from source to remote regions. Recently, PAN total columns have been retrieved from the radiance spectra recorded by IASI (Infrared Atmospheric Sounding Interferometer) onboard the Metop satellite platforms, using a neural network-based retrieval approach. The daily global distributions obtained from these measurements provide a comprehensive picture of PAN through the troposphere.</p><p>Here we exploit as a climatology the 13-year time series of global PAN measurements derived from the IASI/Metop-A observations (October 2007 - December 2020) to characterize the spatial distribution and seasonal variability of PAN abundance worldwide. In particular, continental areas within the tropics appear to be source regions of PAN throughout the year, whereas PAN at North Hemisphere mid- and high latitudes exhibits a more pronounced seasonal cycle and peaks during the boreal summer. Strong outflows of PAN are captured over the oceans, downwind of continental source regions such as Eastern Asia and Eastern US. This dataset also allows us to investigate the recent trends of atmospheric PAN abundance over the last 13 years, over both source and remote areas.</p><p>To better understand what drives the spatial distribution and variability of PAN, we analyze alongside the regional time series of PAN those of carbon monoxide (CO) from IASI/Metop-A, and of formaldehyde (HCHO) and nitrogen dioxide (NO<sub>2</sub>) from OMI/Aura (Ozone Monitoring Instrument). Locally, we find simultaneous enhancements of PAN and CO abundances, which in this case indicates that most PAN originates from fire-derived precursors. This mainly occurs over the typical biomass burning regions in the tropics. Overall, strong correlations are observed over source areas between PAN and HCHO, which is used here as a tracer of tropospheric chemistry and of the presence of oxygenated volatile organic compounds (OVOCs), while there is no particular correlation with NO<sub>2</sub>. The preliminary results suggest that PAN distribution and seasonality is primarily driven by the availability in OVOCs, and hence in peroxyacetyl radical, and that a locally weak NO<sub>2</sub> abundance does not prevent the formation of PAN.</p>

scholarly journals Asymmetry and pathways of inter-hemispheric transport in the upper troposphere and lower stratosphere

2020 ◽  
Author(s):  
Xiaolu Yan ◽  
Paul Konopka ◽  
Marius Hauck ◽  
Aurélien Podglajen ◽  
Felix Ploeger
Keyword(s):  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Boundary Surface ◽  
Lagrangian Model ◽  
Boreal Summer ◽  
Upper Troposphere ◽  
Source Regions ◽  
Mass Fractions ◽  
Asian Summer ◽  
The Tropics

Abstract. Inter-hemispheric transport may strongly affect the trace gas composition of the atmosphere, especially in relation to anthropogenic emissions which originate mainly in the Northern Hemisphere. This study investigates the transport from the boundary surface layer of the Northern Hemispheric (NH) extratropics (30–90° N), Southern Hemispheric (SH) extratropics (30–90° S), and tropics (30° S–30° N) into the global upper troposphere and lower stratosphere (UTLS) using simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In particular, we diagnose inter-hemispheric transport in terms of the air mass fractions (AMF), age spectra, and the mean age of air (AoA) calculated for these three source regions. We find that the AMFs from the NH extratropics to the UTLS are about five times larger than the corresponding contributions from the SH extratropics and almost twenty times smaller than those from the tropics. The amplitude of the AMF seasonal variability originating from the NH extratropics is comparable to that from the tropics. The NH and SH extratropics age spectra show much stronger seasonality compared to the seasonality of the tropical age spectra. The transit time of NH extratropical origin air to the SH extratropics is longer than vice versa. The asymmetry of the inter-hemispheric transport is mainly driven by the Asian summer monsoon (ASM). Both ASM and westerly ducts affect the cross hemispheric transport of the NH extratropical air to the SH, and it is an interplay between the ASM and westerly ducts which triggers such cross-equator transport from boreal summer to fall, mainly westerly ducts over the eastern Atlantic.

scholarly journals Asymmetry and pathways of inter-hemispheric transport in the upper troposphere and lower stratosphere

2021 ◽  
Vol 21 (9) ◽  
pp. 6627-6645
Author(s):  
Xiaolu Yan ◽  
Paul Konopka ◽  
Marius Hauck ◽  
Aurélien Podglajen ◽  
Felix Ploeger
Keyword(s):  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Boundary Surface ◽  
Lagrangian Model ◽  
Boreal Summer ◽  
Upper Troposphere ◽  
Source Regions ◽  
Mass Fractions ◽  
Asian Summer ◽  
The Tropics

Abstract. Inter-hemispheric transport may strongly affect the trace gas composition of the atmosphere, especially in relation to anthropogenic emissions, which originate mainly in the Northern Hemisphere. This study investigates the transport from the boundary surface layer of the northern hemispheric (NH) extratropics (30–90∘ N), southern hemispheric (SH) extratropics (30–90∘ S), and tropics (30∘ S–30∘ N) into the global upper troposphere and lower stratosphere (UTLS) using simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In particular, we diagnose inter-hemispheric transport in terms of the air mass fractions (AMFs), age spectra, and the mean age of air (AoA) calculated for these three source regions. We find that the AMFs from the NH extratropics to the UTLS are about 5 times larger than the corresponding contributions from the SH extratropics and almost 20 times smaller than those from the tropics. The amplitude of the AMF seasonal variability originating from the NH extratropics is comparable to that from the tropics. The NH and SH extratropical age spectra show much stronger seasonality compared to the seasonality of the tropical age spectra. The transit time of NH-extratropical-origin air to the SH extratropics is longer than vice versa. The asymmetry of the inter-hemispheric transport is mainly driven by the Asian summer monsoon (ASM). We confirm the important role of ASM and westerly ducts in the inter-hemispheric transport from the NH extratropics to the SH. Furthermore, we find that it is an interplay between the ASM and westerly ducts which triggers such cross-Equator transport from boreal summer to fall in the UTLS between 350 and 370 K.

scholarly journals Asymmetry and pathways of inter-hemispheric transport in the upper troposphere and lower stratosphere

2021 ◽  
Author(s):  
Xiaolu Yan ◽  
Paul Konopka ◽  
Marius Hauck ◽  
Aurélien Podglajen ◽  
Felix Ploeger
Keyword(s):  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Boundary Surface ◽  
Lagrangian Model ◽  
Boreal Summer ◽  
Upper Troposphere ◽  
Source Regions ◽  
Mass Fractions ◽  
Asian Summer ◽  
The Tropics

<p>Inter-hemispheric transport may strongly affect the trace gas composition of the atmosphere, especially in relation to anthropogenic emissions which originate mainly in the Northern Hemisphere. This study investigates the transport from the boundary surface layer of the Northern Hemispheric (NH) extratropics (30-90<sup>o</sup>N), Southern Hemispheric (SH) extratropics (30-90<sup>o</sup>S), and tropics (30<sup>o</sup>S-30<sup>o</sup>N) into the global upper troposphere and lower stratosphere (UTLS) using simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In particular, we diagnose inter-hemispheric transport in terms of the air mass fractions (AMF), age spectra, and the mean age of air (AoA) calculated for these three source regions. We find that the AMFs from the NH extratropics to the UTLS are about five times larger than the corresponding contributions from the SH extratropics and almost twenty times smaller than those from the tropics. The amplitude of the AMF seasonal variability originating from the NH extratropics is comparable to that from the tropics. The NH and SH extratropics age spectra show much stronger seasonality compared to the seasonality of the tropical age spectra. The transit time of NH extratropical origin air to the SH extratropics is longer than vice versa. The asymmetry of the inter-hemispheric transport is mainly driven by the Asian summer monsoon (ASM). We confirm the important role of ASM and westerly ducts in the inter-hemispheric transport from the NH extratropics to the SH. However, we find that it is an interplay between the ASM and westerly ducts which triggers such cross-equator transport from boreal summer to fall, mainly westerly ducts over the eastern Atlantic.</p>

scholarly journals Road Short-Term Travel Time Prediction Method Based on Flow Spatial Distribution and the Relations

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Mingjun Deng ◽  
Shiru Qu
Keyword(s):  
Time Series ◽  
Spatial Distribution ◽  
Travel Time ◽  
Nonparametric Regression ◽  
Nearest Neighbor ◽  
Nearest Neighbor Search ◽  
Short Term ◽  
Combination Model ◽  
The Road ◽  
Neighbor Search

There are many short-term road travel time forecasting studies based on time series, but indeed, road travel time not only relies on the historical travel time series, but also depends on the road and its adjacent sections history flow. However, few studies have considered that. This paper is based on the correlation of flow spatial distribution and the road travel time series, applying nearest neighbor and nonparametric regression method to build a forecasting model. In aspect of spatial nearest neighbor search, three different space distances are defined. In addition, two forecasting functions are introduced: one combines the forecasting value by mean weight and the other uses the reciprocal of nearest neighbors distance as combined weight. Three different distances are applied in nearest neighbor search, which apply to the two forecasting functions. For travel time series, the nearest neighbor and nonparametric regression are applied too. Then minimizing forecast error variance is utilized as an objective to establish the combination model. The empirical results show that the combination model can improve the forecast performance obviously. Besides, the experimental results of the evaluation for the computational complexity show that the proposed method can satisfy the real-time requirement.

scholarly journals Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012

2016 ◽  
Author(s):  
Norbert Glatthor ◽  
Michael Höpfner ◽  
Adrian Leyser ◽  
Gabriele P. Stiller ◽  
Thomas von Clarmann ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Michelson Interferometer ◽  
Austral Summer ◽  
Emission Spectra ◽  
Set Covering ◽  
Boreal Summer ◽  
Systematic Bias ◽  
High Latitudes ◽  
Data Set ◽  
The Tropics

Abstract. We present a global OCS data set covering the period June 2002 to April 2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. The vertical resolution is 4–5 km in the height region 6–15 km and 15 km at 40 km altitude. The total estimated error amounts to 40–50 pptv between 10 and 20 km and to 120 pptv at 40 km altitude. MIPAS OCS data show no systematic bias with respect to balloon observations, with deviations mostly below ±50 pptv. However, they are systematically higher than the OCS volume mixing ratios of the ACE-FTS instrument on SCISAT, with maximum deviations of up to 100 pptv in the altitude region 13–16 km. The data set of MIPAS OCS exhibits only moderate interannual variations and low interhemispheric differences. Average concentrations at 10 km altitude range from 480 pptv at high latitudes to 500–510 pptv in the tropics and at northern mid-latitudes. Seasonal variations at 10 km altitude amount up to 35 pptv in the northern and up to 15 pptv in the southern hemisphere. Northern hemispheric OCS abundances at 10 km altitude peak in June in the tropics and around October at high latitudes, while the respective southern hemispheric maxima were observed in July and in November. Global OCS distributions at 250 hPa (~ 10–11 km) show enhanced values at low latitudes, peaking during boreal summer above the western Pacific and the Indian Ocean, which indicates oceanic release. Further, a region of depleted OCS amounts extending from Brazil to central and southern Africa was detected at this altitude, which is most pronounced in austral summer. This depletion is related to seasonally varying vegetative uptake by the tropical forests. Typical signatures of biomass burning like the southern hemispheric biomass burning plume are not visible in MIPAS data, indicating that this process is only a minor source of tropospheric OCS. At the 150 hPa level (~ 13–14 km) enhanced amounts of OCS were also observed inside the Asian Monsoon Anticyclone, but this enhancement is not especially outstanding as compared to other low latitude regions at the same altitude. At the 80 hPa level (~ 17–18 km) equatorward transport of mid-latitude air masses containing lower OCS amounts around the summertime anticyclones was observed. A significant trend could not be detected in tropospheric MIPAS OCS amounts, which points to globally balanced sources and sinks.

scholarly journals Initiation of Boreal Summer Intraseasonal Oscillation: Dynamic Contribution by Potential Vorticity

2012 ◽  
Vol 140 (6) ◽  
pp. 1748-1760 ◽  
Author(s):  
Kyong-Hwan Seo ◽  
Eun-Ji Song
Keyword(s):  
Potential Vorticity ◽  
Intraseasonal Oscillation ◽  
Vertical Wind Shear ◽  
Boreal Summer ◽  
Dynamical Process ◽  
Initiation Mechanism ◽  
Middle Troposphere ◽  
Boreal Summer Intraseasonal Oscillation ◽  
Low Level ◽  
The Tropics

Abstract Potential vorticity (PV) thinking conceptually connects the upper-level (upper troposphere in the extratropics and middle troposphere for the tropics) dynamical process to the lower-level process. Here, the initiation mechanism of the boreal summer intraseasonal oscillation (BSISO) in the tropics is investigated using PV thinking. The authors demonstrate that the midtropospheric PV anomaly produces a dynamical environment favorable for the BSISO initiation. Under seasonal easterly vertical wind shear, the PV anomaly enhances low-level convergence and upward motion at its western edge. Tropical PV forcing in the middle troposphere produces balanced mass and circulation fields that spread horizontally and vertically so that its effect can reach even the lowest troposphere. The downward influence of the midtropospheric PV forcing is one of the key aspects of the PV thinking. Direct piecewise PV inversions confirm that the anomalous lower-level zonal wind and its convergence necessary for the initiation of BSISO convection do not arise solely from the response to the lower-level PV forcing but from the summed contribution by PV forcing at all levels. About 50% of the low-level circulation variations result from PV forcing from 700 to 450 hPa, with the largest contribution from the 600–650-hPa PV anomalies for the convection initiation region over the western Indian Ocean. The current study is compared with and incorporated into the thermodynamic recharge process and the frictional moisture flux convergence mechanism for the BSISO initiation. This study is the first qualitative application of the PV thinking approach that reveals the BSISO dynamics.

scholarly journals Construction of merged satellite total O<sub>3</sub> and NO<sub>2</sub> time series in the tropics for trend studies and evaluation by comparison to NDACC SAOZ measurements

2014 ◽  
Vol 7 (10) ◽  
pp. 3337-3354 ◽  
Author(s):  
M. Pastel ◽  
J.-P. Pommereau ◽  
F. Goutail ◽  
A. Richter ◽  
A. Pazmiño ◽  
...  
Keyword(s):  
Time Series ◽  
Lower Stratosphere ◽  
Atmospheric Composition ◽  
Data Sets ◽  
Composition Change ◽  
Long Time ◽  
Uv Visible ◽  
The Tropics ◽  
Lower Noise ◽  
Total Column

Abstract. Long time series of ozone and NO2 total column measurements in the southern tropics are available from two ground-based SAOZ (Système d'Analyse par Observation Zénithale) UV-visible spectrometers operated within the Network for the Detection of Atmospheric Composition Change (NDACC) in Bauru (22° S, 49° W) in S-E Brazil since 1995 and Reunion Island (21° S, 55° E) in the S-W Indian Ocean since 1993. Although the stations are located at the same latitude, significant differences are observed in the columns of both species, attributed to differences in tropospheric content and equivalent latitude in the lower stratosphere. These data are used to identify which satellites operating during the same period, are capturing the same features and are thus best suited for building reliable merged time series for trend studies. For ozone, the satellites series best matching SAOZ observations are EP-TOMS (1995–2004) and OMI-TOMS (2005–2011), whereas for NO2, best results are obtained by combining GOME version GDP5 (1996–2003) and SCIAMACHY – IUP (2003–2011), displaying lower noise and seasonality in reference to SAOZ. Both merged data sets are fully consistent with the larger columns of the two species above South America and the seasonality of the differences between the two stations, reported by SAOZ, providing reliable time series for further trend analyses and identification of sources of interannual variability in the future analysis.

scholarly journals Detection of multi-layer and vertically-extended clouds using A-train sensors

2009 ◽  
Vol 2 (5) ◽  
pp. 2707-2748 ◽  
Author(s):  
J. Joiner ◽  
A. P. Vasilkov ◽  
P. K. Bhartia ◽  
G. Wind ◽  
S. Platnick ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Simple Algorithm ◽  
Ozone Monitoring Instrument ◽  
Infrared Observations ◽  
Summer Hemisphere ◽  
Moderate Resolution ◽  
Cloud Optical Thickness ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Tropics ◽  
Cloud Top Pressure

Abstract. The detection of multiple cloud layers using satellite observations is important for retrieval algorithms as well as climate applications. In this paper, we describe a relatively simple algorithm to detect multiple cloud layers and distinguish them from vertically-extended clouds. The algorithm can be applied to coincident passive sensors that derive both cloud-top pressure from the thermal infrared observations and an estimate of solar photon pathlength from UV, visible, or near-IR measurements. Here, we use data from the A-train afternoon constellation of satellites: cloud-top pressure, cloud optical thickness, and the multi-layer flag from the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) and the optical centroid cloud pressure from the Aura Ozone Monitoring Instrument (OMI). The cloud classification algorithms applied with different passive sensor configurations compare well with each other as well as with data from the A-train CloudSat radar. We compute monthly mean fractions of pixels containing multi-layer and vertically-extended clouds for January and July 2007 at the OMI spatial resolution (12 km×24 km at nadir) and at the 5 km×5 km MODIS resolution for infrared cloud retrievals. There are seasonal variations in the spatial distribution of the different cloud types. The fraction of pixels containing distinct multi-layer cloud is a strong function of the pixel size. Globally averaged, these fractions are approximately 20% and 5% for OMI and MODIS, respectively. These fractions may be significantly higher or lower depending upon location. There is a much smaller resolution dependence for fractions of pixels containing vertically-extended clouds (~20% for OMI and slightly less for MODIS globally), suggesting larger spatial scales for these clouds. We also find significantly higher fractions of vertically-extended clouds over land as compared with ocean, particularly in the tropics and summer hemisphere.

scholarly journals Coastal Wave Extremes around the Pacific and Their Remote Seasonal Connection to Climate Modes

Climate ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 168
Author(s):  
Julien Boucharel ◽  
Loane Santiago ◽  
Rafael Almar ◽  
Elodie Kestenare
Keyword(s):  
Large Scale ◽  
Wind Wave ◽  
Boreal Summer ◽  
Opposite Hemisphere ◽  
Ocean Surface Waves ◽  
First Order ◽  
Coastal Waves ◽  
The Pacific ◽  
Wide Range ◽  
The Tropics

At first order, wind-generated ocean surface waves represent the dominant forcing of open-coast morpho-dynamics and associated vulnerability over a wide range of time scales. It is therefore paramount to improve our understanding of the regional coastal wave variability, particularly the occurrence of extremes, and to evaluate how they are connected to large-scale atmospheric regimes. Here, we propose a new “2-ways wave tracking algorithm” to evaluate and quantify the open-ocean origins and associated atmospheric forcing patterns of coastal wave extremes all around the Pacific basin for the 1979–2020 period. Interestingly, the results showed that while extreme coastal events tend to originate mostly from their closest wind-forcing regime, the combined influence from all other remote atmospheric drivers is similar (55% local vs. 45% remote) with, in particular, ~22% coming from waves generated remotely in the opposite hemisphere. We found a strong interconnection between the tropical and extratropical regions with around 30% of coastal extremes in the tropics originating at higher latitudes and vice-versa. This occurs mostly in the boreal summer through the increased seasonal activity of the southern jet-stream and the northern tropical cyclone basins. At interannual timescales, we evidenced alternatingly increased coastal wave extremes between the western and eastern Pacific that emerge from the distinct seasonal influence of ENSO in the Northern and SAM in the Southern Hemisphere on their respective paired wind-wave regimes. Together these results pave the way for a better understanding of the climate connection to wave extremes, which represents the preliminary step toward better regional projections and forecasts of coastal waves.

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